1. Field of the Invention
The present invention is generally related to an accelerometer and, more particularly, to an accelerometer in which a magnet structure is attached to a distal end of a cantilever beam that is formed as an integral part of a housing structure.
2. Description of the Prior Art
Many different types of accelerometers are known to those skilled in the art. U.S. Pat. No. 5,036,705, which issued to Gaines on Aug. 6, 1991, discloses an accelerometer that is damped with a self contained viscous material. It provides a damping arrangement for a deflectable beam accelerometer where the deflectable end of the beam is spaced from a stationary member. A drop of self contained viscous material extends between the deflectable end of the beam and the stationary member in order to dampen the movement of the deflectable end.
U.S. Pat. No. 4,321,464, which issued to Miller on Mar. 23, 1982, describes a device for measuring vibration phase and amplitude. The device is used for measuring vibration and comprises a vane that is attached to a vibratory member. A light supply is provided and at least one detector is used. The vane includes, or is attached to, a mask having a plurality of light directing and light opaque elements. During vibration, the mask travels transversely of the light path. The elements of the mask may be encoded, as with a Gray Code, so as to yield both amplitude and phase information. The elements may be so arranged as to chop the light into a plurality of pulses for each vibration of the vane through the use of a second stationary mass. In either case, the device yields information whose interpretation is substantially independent of fluctuations in the intensity of the source light.
U.S. Pat. No. 4,967,598, which issued to Wakatsuki et al on Nov. 6, 1990, describes an acceleration sensor that includes an cantilever beam having a free end to which a permanent magnet is attached. A pair of magnetic sensors, each comprising a barber-pole type magnetoresistive sensing element, is arranged in symmetrically spaced and opposed relationship and in a common plane extending parallel to the magnetic flux of the permanent magnet with respect to opposite sides of the magnet. The cantilever is bent and the magnet is moved accordingly in response to an acceleration force, which is detected as outputs from the magnetoresistive sensing elements.
U.S. patent application Ser. No. 08/142,753 (M40-15406), which was filed on Oct. 25, 1993 by Henrion and assigned to the assignee of the present application, describes an accelerometer that is provided with a proof mass attached to a movable plate that is rotatable about an axis that lies in the plane of a silicon substrate. The first and second portions of a movable conductor are provided on the rotatable plate and first and second stationary conductors are disposed in association with the first and second portions in order to provide two capacitors. The capacitors can be used to measure the rotational movement of the movable conductor and can also be used to create electromotor force to force rebalance the plate in response to acceleration forces exerted on the center of mass of the proof mass. The proof mass is displaced above the rotational plate and therefore is responsive to accelerations in a direction parallel to the plane of the substrate and of the rotatable plate. This permits two accelerometers to be simultaneously manufactured in a single silicon substrate in order to measure accelerations in two perpendicular directions, wherein both of the directions lie in the plane of the substrate. Acceleration forces on the proof mass cause the movable plate to rotate about its support axis and change the capacitance effect of both capacitors. Alternative embodiments of the accelerometer can utilize piezoresistors disposed on the support arms instead of relying solely on the capacitor techniques described above.
Many accelerometers known to those skilled in the art require costly assembly procedures which increase the cost of the accelerometer and therefore inhibit its use in many applications which do not justify the inclusion of an expensive accelerometer. It would therefore be advantageous if an accelerometer could be developed which can be manufactured inexpensively while maintaining the ability to accurately determine the acceleration of a device to which the accelerometer is attached.